Frozen aerated food products, to which this invention is directed include frozen desserts such as ice cream, ice milk, mellorine, sherbet, frozen custard, frozen pudding and the like, frozen shake beverages such as milk shakes, mousse, yogurt and frozen shake concentrate. The popularity of these products is attributable to their convenience, widespread availability, nutritive value and appealing forms, colors and flavors. In part, due to the familiarity of such frozen products to the consumer, to be acceptable they must not only have suitable flavor and appearance, but also possess a complex set of physical properties which provide the characteristics which consumers have come to expect. In addition, the nature and composition of the most popular aerated frozen products are set by various standards promulgated by the U.S. Food and Drug Administration as well as the individual states. Such rigid consumer acceptance criteria, regulatory standards and the complex nature of the interactions which produce a satisfactory product make it extremely difficult to reformulate such aerated frozen products in an attempt to provide improvements. Solutions to one set of problems quite often generate other problems which make the product unacceptable.
Foam stability of conventional aerated frozen desserts is a major problem. Ice cream and related aerated frozen desserts are stored, distributed, delivered and sold at deep freeze temperatures, i.e. -20.degree. F. (-29.degree. C.), to give some measure of stability to these products and protect their special textural properties. Economically, 0.degree. F. (-18.degree. C.) distribution systems are more feasible and available. At 0.degree. F. (-18.degree. F.) distribution system, one major problem is that temperature fluctuations invariably occur which can result in the thawing and refreezing of the product, seriously deteriorating its quality over time. In home freezers and conventional freezing dispensing chambers temperature fluctuation can also be very severe. The "heat shock" to the frozen products from these fluctuations is characterized by the formation of large ice crystals and big air cells, and results in a coarse, gloss appearance and gritty mouthfeel. Heat shock frequently also produces a separation of the syrupy aqueous phase from the air and fat matrix which ultimately make the appearance and texture of the product unacceptable.
Another problem with foam products is that at deep freeze and household freezer temperatures the product is so hard that it is difficult to scoop and serve immediately from the freezer. Hardness at these levels are easier to achieve and help stabilize the products which is good for producers but a detriment to consumers.
Several solutions to these problems have been attempted in the past. For example, increased stability has been imparted to aerated frozen desserts through the use of various stabilizers and stabilizer combinations. The drawback of this approach is that stabilizers frequently are required in such great quantities that the feel of the product in the mouth is altered, producing a cloying, gummy or greasy sensation. Another approach has been to increase the amount of added sugars relative to the fat and/or water in the product, but the large amount of sugar required to provide acceptable stability often results in too sweet a taste or unacceptable crystal formation. Still another approach has been to increase the amount of incorporated air, i.e., "overrun", and thereby decrease the amount of freezable water per unit volume. This attempt at reformulation, however, not only results in a texture which is more characteristic of a whipped topping than of a frozen dessert like ice cream, but is limited by the applicable standards of identity relating to required weight per volume and solids content.
As a result of the instability of most aerated frozen desserts, producers have been required to manufacture the products locally to avoid the long periods of storage and temperature variations which are associated with national distribution from a few centrally located plants. Since most producers, distributors and retailers rely on deep freeze temperatures for preserving the quality of ice cream-type frozen desserts during storage, distribution and sale, totally separate systems are required for such products than are used for other frozen foods, which can be distributed at temperatures ranging from 0.degree. F. (-18.degree. C.) to 10.degree. F. (-12.degree. C.). A very extensive network of frozen food storage, distribution and retailing facilities has been established nationwide, and therefore it can be seen that it would be extremely advantageous from an economic and efficiency standpoint if an ice cream-type and other types of aerated frozen dessert of acceptable quality and stability could also utilize this system.
Milkshakes and similar frozen shake beverages are representative of another type of aerated frozen food product in which poor stability has limited the storage and distribution systems which the manufacturer can utilize. As is well-known, milkshakes are usually manually prepared or dispensed from a commercial establishment for consumption on the premises. Various attempts have been made in the past to provide products which are more widely available or are more susceptible to automated procedures. For example, milkshakes have simply been packaged in individual cups and frozen solid for distribution. The product is then warmed under controlled conditions to room temperature, agitated or otherwise mixed, and served. Another approach has been to prepare and distribute a frozen milkshake concentrate which serves as a base to which milk or water is added with agitation. Still another approach has been to aseptically can or bottle a prepared milkshake which is consumed after being chilled, shaken and opened. All of these prior approaches have either required unacceptably large amounts of time or space, required a reconstitution step which is either difficult or time-consuming and/or have provided milkshakes which do not have the desired creaminess, coldness and consistency of commercially prepared milkshakes.
Since shakes are extremely popular items at fast food restaurants, it is of course important to reduce the time and labor involved in preparing large quantities of shakes manually. The present invention provides shakes with improved stability which can be prepared in individual containers in central locations and shipped in a frozen state to various restaurant locations where they are stored and served at refrigeration temperatures without any on-site preparation.
Accordingly, it is an object of this invention to provide aerated frozen food products which are stable for sufficient periods of time to allow national distribution under conditions and temperatures encountered in 0.degree. F. (-18.degree. C.) frozen food systems. Another object is to provide an aerated frozen product which attains the aforesaid stability without a basic reformulation which would bring the product outside the limits of consumer acceptance and regulatory standards. A still further object of the invention is to provide aerated frozen dessert products having the above attributes which are also soft and scoopable at freezer temperatures. Another object is to provide shakes and similar beverages having the above attributes which retain the desirable characteristics of commercially prepared milkshakes when served at refrigeration temperatures (e.g. 15.degree. F. (-9.5.degree. C.) to 25.degree. F. (-4.degree. C.)). A related object is to provide a frozen shake concentrate which can readily be reconstituted by the consumer into a high-quality shake.